1. Field of the Invention
This invention relates to a photosensitive member, and more particularly, to a photosensitive member having a photosensitive layer containing a novel organic photoconductive material composed of a hydrazone compound having a benzimidazole ring.
2. Description of the Prior Art
As photoconductive materials used for electrophotosensitive members, a variety of inorganic photoconductive materials such as selenium, cadmium sulfide, and zinc oxide are known. These photoconductive materials have many advantages such as charging to an appropriate voltage in the dark, less dissipation of charge in the dark, rapid dissipation of charge when irradiated with a light, and the like.
On the contrary, these photoconductive materials suffer from various drawbacks. For example, selenium photosensitive members are adversely affected by temperature, humidity, dust, pressure and the like, and crystallization of selenium easily proceeds, in particular, when the ambient temperature exceeds 40.degree. C., the crystallization markedly proceeds and there occur various disadvantages such as lowering of chargeability and formation of white spots in the image. When selenium photosensitive members and cadmium sulfide photosensitive members are used under high humidity for a long time, stable sensitivity and durability can not be obtained.
Zinc oxide photosensitive members require dye sensitizers such as Rose Bengal and the like to be sensitized, but such dye sensitizers are deteriorated by corona charging and faded by irradiation light, and therefore it is not possible produce stable images over a long period of time.
On the contrary, there have been proposed a wide variety of organic photoconductive polymers such as polyvinylcarbazoles and the like. Those organic photoconductive polymers are excellent in film-shapeability and light weight as compared with the above-mentioned inorganic photoconductive materials, but the polymers have not yet been practically used since the film-shapeability is not sufficient for practical purposes and, in addition, the sensitivity, durability and stability under changeable environment are poorer than those of inorganic photoconductive materials.
Low molecular weight organic photoconductive materials are proposed, for example, p-diethylaminobenzaldehyde-(diphenylhydrazone) and 1-phenyl-3-(p-diethylaminostyryl)-5-(p-diethylaminophenyl) pyrazoline are proposed by U.S. Pat. Nos. 4,150,987 and 3,837,851, respectively. When an appropriate binder is selected for such low molecular weight organic photoconductive materials, the film-shapeability can be improved to a great extent which is a big problem in the field or organic photoconductive polymers, but the sensitivity is still insufficient.